已知扇形的半径为12，弧长为18，则扇形圆心角为（）A．23B．2π3C．32D．3π2

Question

已知扇形的半径为12，弧长为18，则扇形圆心角为（　　）

A．(2)/(3)
B．(2π)/(3)
C．(3)/(2)
D．(3π)/(2)

(2)/(3)
B．(2π)/(3)
C．(3)/(2)
D．(3π)/(2)(2)/(3)2233
(2π)/(3)
C．(3)/(2)
D．(3π)/(2)(2π)/(3)2π2π33
(3)/(2)
D．(3π)/(2)(3)/(2)3322
(3π)/(2)(3π)/(2)3π3π22

Answer 1

设扇形圆心角为α，则
∵扇形的半径为12，弧长为18，
∴α＝(l)/(r)＝(18)/(12)＝(3)/(2)．
故选C． α＝(l)/(r)lllrrr＝(18)/(12)181818121212＝(3)/(2)333222．
故选C．